in alcohol, had a single dark purple pigment father were more soluble and had a similar polarity to their solvents. (Paper chromatography lab sheet)

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1 Zalewski 1 Analyzing Pigments in Inks Through Paper Chromatography Submitted by: Melissa Zalewski Submitted to: Mrs. McGuckin Course Code: SCH 3UP Date: Thursday, October 20, 2016 Abstract The aim of this experiment was to run a paper chromatography test to analyze three inks from various sources by viewing the results and calculating their Rf values. During a test, the stationary phase, the chromatography paper, hold the ink until the mobile phase (the solvent and solutes) passes. Due to the different affinities of the components of the ink, they can be separated and analyzed. None of the three inks tested in my group shared pigments. The ink, tested in water, had four bright components with Rf values from 0.39 to 0.98; the pen, tested in water as well, had a yellow pigment with 0.05 Rf; the permanent Sharpie marker, tested in alcohol, had a single dark purple pigment with 1.00 Rf. Pigments that travelled father were more soluble and had a similar polarity to their solvents. (Paper chromatography lab sheet) Purpose The purpose of this lab was to run a paper chromatography test using different inks from various sources, to then calculate the R f value for each pigment component upon viewing the results of the test, and finally to determine the presence of any common pigments among samples. Hypothesis If the three inks tested do in fact share pigments, then the R f values and visual chromatography results will be similar, because chemicals made of the same entities will have similar solubility and polarities, allowing them to travel similar distances due to affinity with the paper and the solvent. Materials and Equipment Eye dropper Chromatography paper, one strip per sample Pencil Water (solvent) Isopropyl alcohol (solvent) Various pens, inks, and markers (solutes): Liquid ink Pen (Bic Ultra Round Stic Grip pen) Permanent marker (Sharpie)

2 Zalewski 2 Procedure 1. A horizontal straight line, the starting line, was drawn 1.5 cm up from the bottom of each strip of chromatography paper. A second horizontal line, the ending line, was drawn 0.5 cm from the tops of the strips. 2. A large dot was drawn on each starting line with a sample from each ink. The eye dropper was used for the liquid ink. 3. A test tube for each strip (a total of three test tubes) was filled up to 0.5 cm with alcohol (for the permanent marker) or water (for the pen and ink). 4. Each chromatography paper strip with an ink sample was submerged into its respective test tube. The solution was not allowed to reach the starting lines or ink samples. 5. The solution was allowed approximately 20 minutes to seep up the paper. After this each chromatography strip was removed from its test tube. 6. A sketch was made of each result, showing the distance the solvent and each of the pigments had travelled. 7. The R f value for each separated pigment was calculated. Results Tabled Results of Paper Chromatography for Three Different Inks Solute Solvent Pigments R f Value Distances Permanent Marker (Sharpie) Pen (Bic Ultra Round Stic Grip pen) Alcohol Purple 1.0 R f 4.5cm Water Yellow 0.05 R f 0.5cm Ink Water Light blue 0.39 R f 9.3cm Reddish-pink 0.62 R f 8.1cm Yellowish-green 0.92 R f 5.9cm Blue 0.98 R f 3.7cm Sketched Results of Paper Chromatography for Three Different Inks

3 Zalewski 3 Permanent Marker/Sharpie (In Alcohol) Pen (In Water)

4 Zalewski 4 Ink (In Water) Sample Calculations Sharpie, purple pigment: 4.5cm = 1.0 R f Ink, purple pigment: 4.5cm Pen, yellow pigment: 0.5 cm = 0.05 R f Pen, yellow pigment: 10.5cm Ink, light blue pigment: 3.7cm = 0.39 R f Ink, light blue pigment: 9.5 cm Ink, reddish-pink pigment: 5.9cm = 0.62 R f Ink, reddish-pink pigment: 9.5cm Ink, yellowish-green pigment: 8.1cm = 0.92 R f Ink, reddish-pink pigment: 9.5cm Ink, blue pigment: 9.3cm = 0.98 R f Ink, reddish-ment: 9.5cm

5 Zalewski 5 Discussion Based on the results collected, none of the three inks tested in this particular lab shared any pigments. The results of the chromatography were visually different in both colour and distance travelled, and the R f values were all drastically different. Both these factors signify that all pigments are made with different chemicals and are not the same substances. However after the lab it became apparent that the second ink tested, the pen in water, was, in fact, insoluble in water, and would have brought clearer results had it been tested with alcohol. It only showed a faint yellow pigment that only traveled 0.5cm, while the solvent traveled 10.5cm. The other two inks tested were much more accurate. The permanent Sharpie marker, tested with alcohol, was not composed of many pigments, only an indigo that ran an equal distance to the solvent. This means it is very soluble in alcohol and has a similar polarity, thus less polar than water; one knows this due to the general rule of like polarities dissolving like polarities. The liquid ink, tested with water, was composed of many vibrant and varied pigments, ranging from blue with an R f value of 0.98, to light blue with an R f value of This means that certain pigments are very polar, almost equally to water, and are thus very attracted to that solvent, dissolving and travelling a greater distance. Other pigments must be less polar and soluble, and are not as attracted or capable of dissolution in water. They therefore do not travel as far. This lab clearly shows the concepts of adhesive forces, which are between molecules of a liquid and those of a surface; cohesive forces, which bind similar molecules together, and surface tension. The father a pigment travels, the more powerful its adhesive forces to the solvent are, allowing it to overcome its surface tension and cohesion and travel, through capillary action, between the porous spaces of the chromatography paper, the stationary phase. Pigments and solvents with like polarities are more likely to bond together, due to more equal dipole-dipole forces, making them attracted enough to the solvent to be able to spread out and travel a longer distance. Less polar compounds are more hydrophobic, and more attracted to less polar solvents. If the cohesive forces are more powerful, the pigment retains more of its surface tension, does not dissolve or spread out, and travels a shorter distance, especially if has a vastly different polarity from the solvent. (Haberer, 2011)

6 Zalewski 6 Analyses like this are used very often in the field of forensics, even with substances as seemingly innocent as pens. For example, ink chromatography may be used in order to determine whether a pen belonging to a suspect was used to write a note found at a crime scene. Other forms of chromatography can be used to identify and compare other substances in this field, such as drugs, ambiguous stains, gaseous substances, or incriminating trace evidence. This specific type of test can also be used by companies manufacturing inks to see which pigments contribute to better performance, or simply the similarities between various ink products. (Lee, 2015) Discussion: Comparison The results were compared with those of other groups from the same lab; most results were quite different due to the variety of inks tested. For example, one group tested a yellow highlighter which was composed of only yellow pigment but did not test a Bic pen, so the results were incomparable. One constant among the groups was the pure ink, tested in water. For each group, the results were similar. Additionally, a second group also tested a Sharpie marker in water, receiving similar results to those discussed in this report. In both cases, slight variations exist due to inconsistency in the length of time left for the mobile phase to run. When compared against the results of a Sharpie marker tested with rubbing alcohol for six minutes (outside of this lab), a similar single indigo pigment was produced, confirming the results from this lab. It did run a shorter distance, but this can be attributed to the shorter run time. (Matias, 2013) Discussion: Analysis of Experiment This experiment was not a fair test. It was not objective because those conducting the experiment were not blind to the origins of the inks. Each variable, within each group and the whole classroom, were tested for slightly different amounts of time, skewing the results and making it harder to compare them, both their visual appearance and their R f values. Inconsistent amounts of ink were tested as well, further skewing the data. Finally, the experiments were not repeated, having only been tested once, and therefore allowed room for error that could have been eliminated or minimized by calculating the average R f values for all potential repetitions. However, a strength of the experiment was that it did function relatively well in separating the components of each ink by dissolving and carrying them in the mobile phase, except for the pen, which was not very soluble in water and should have been tested with alcohol to produce clearer

7 Zalewski 7 results. This allowed for rough analysis of the components, though due to the unfair nature of the test the analysis in and of itself was skewed as well. Variables that are uncontrollable are, if anything, very slight, such as small differences in the paper used, which would hinder the passing of the component molecules through the pores, or slight contamination of the solvents, which would affect the solubility of the components into the solvent. Both would change the results and R f values, though not by much, and are very hard, to control. Conclusion To conclude, none of the three inks tested shared pigments, due to the fact that visually they were all different colours, traveled different distances, and quantifiably had different R f values. The ink, tested in water, had four very vibrant colours with R f values ranging from 0.39 to 0.98; the pen, tested in water as well, had a single yellow pigment with an R f value of 0.05; the permanent Sharpie, tested in alcohol, had a single dark purple pigment with an R f value of References Lee, L. C., Yunus, I. S. M. D., Fuad, W. N. S. W. M., Ishak, A. A., & Osman, K. (2015). Statistical discrimination of black ballpoint pen inks using ultra-performance liquid chromatography with principal component analysis. Journal of Analytical Chemistry, 70(3), Retrieved from main&v=2.1&it=r&id=gale%7ca &asid=8a0b51b5820bea5b620cf760e298 9ccd Haberer, S., & DiGiuseppe, M. (2011). Nelson chemistry 11: University preparation. Toronto: Nelson Education. Matias, M. (2013, October 15). Paper chromatography lab [Blog post]. Retrieved from paper-chromatography-lab.html Paper chromatography lab sheet